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AssigneeBorgWarner Inc.
InventorRoger Simpson
Estimating the term…
The cam phaser of the present invention includes an externally mounted DPCS (234) with spool position feedback to control the position of a center mounted spool valve (192) and control the phase angle of the cam mounted phaser. A position sensor (300) is mounted to the spool valve position such that a control loop (400) controls the position of the spool valve (192). A second, outer loop (430) controls the phaser angle. An offset is preferably added to the spool valve position to move the spool valve to its steady state or null position. This null position is required so that the spool (200) can move in to move the phaser in one direction and outward to move the phaser in the other direction. This type of system reduces any frictional or magnetic hysteresis in the system.
A variable cam timing system for an internal combustion engine having a crankshaft, at least one camshaft, a cam drive connected to the crankshaft, and a variable cam phaser having an inner portion mounted to at least one camshaft and a concentric outer portion connected to the cam drive, the relative angular positions of the inner potion and the outer portion being controllable in response to a fluid control input, such that the relative phase of the crankshaft and at least one camshaft can be shifted by varying the fluid at the fluid control input of the variable cam phaser, the variable cam timing system comprising:
An internal combustion engine comprising:
In an internal combustion engine having a variable camshaft timing system for varying phase angle of a camshaft relative to a crankshaft, a method of regulating the fluid flow from a source to a means for transmitting rotary movement from the crankshaft to a housing, comprising the steps of:
Dependencies are inferred from the claim text.
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Characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the…:…
Changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear: by torque-responsive means
Details relating to the hydraulic feeding circuit: oil control valves
Methods of operation using a variable valve timing mechanism
Term end not estimated
1. Field of the Invention
The invention relates to a hydraulic control system for controlling the operation of a variable camshaft timing (VCT) system. More specifically, the present invention relates to a control system that utilizes a position sensor mounted to a differential pressure control system (DPCS) with a centrally mounted spool valve and a control loop controlling the position of the spool valve.
2. Description of Related Art
FIG. 1 is a flow chart of a cam torque actuated variable cam timing device with a differential pressure control system (DPCS).
FIG. 2 is a schematic view of the variable camshaft timing arrangement containing the present invention.
FIG. 3 is a flowchart of a cam torque actuated variable cam timing device with a differential pressure control system (DPCS) and spool valve position feedback of the present invention.
The present invention reduces the error created by the prior art by having a position sensor mounted to the spool valve position, of a differential pressure control system (DPCS), and a feedback control loop controlling the position of the spool valve. This method reduces any frictional or magnetic hysteresis in the system. There is also preferably a second, outer feedback loop to control the phaser angle. The inner loop controls the spool valve position, while the outer loop controls the phase angle. An offset is preferably added to the spool valve position to move the spool valve to its steady state or null position. The null position is required so that the spool can move in to move the phaser in one direction and move out to move the phaser in the other direction. The “phaser” is the variable cam timing (VCT) component, which allows the position of the camshaft (126) to be varied in phase relative to the crankshaft also known as a “cam indexer.”
Pressure and viscosity of the hydraulic fluid that is used in the control system, illustratively engine lubricating oil in an automotive VCT application, can change over a period of time due to changes in the engine rpm, the operating temperature or age of the oil, or variations in the composition of the engine oil from time to time as a result of an oil change in which the old oil is replaced by an oil of a different brand or grade. In a control system that relies on an hydraulic force of variable magnitude to counteract a mechanical force, the actual hydraulic control pressure, which is at least partly related to viscosity in a dynamic system, is maintained at a predetermined value by changing the duty cycle which is inputted into the pulse width modulated (PWM) valve. The PWM valve, is used to control the hydraulic pressure at a reduced level from a higher pressure source, for example, the oil supply, based on the duration of the “on” cycles of the PWM valve relative to its “off” cycles.
FIG. 2 shows a cam phaser of present invention in which a housing in the form of a sprocket (132) is oscillatingly journalled on a camshaft (126). The camshaft (126) may be considered to be the only camshaft of a single camshaft engine, either of the overhead camshaft type or the in block camshaft type. Alternatively, the camshaft (126) may be considered to be either the intake valve operating camshaft or the exhaust valve operating camshaft of a dual camshaft engine. In any case, the sprocket (132) and the camshaft (126) are rotatable together, and are caused to rotate by the application of torque to the sprocket (132) by an endless roller chain, which is trained around the sprocket (132) and also around a crankshaft with its own sprocket. As will be hereinafter described in greater detail, the sprocket (132) is oscillatingly journalled on the camshaft (126) so that is oscillatable at least through a limited arc with respect to the camshaft (126), an action which will adjust the phase of the camshaft (126) relative to the crankshaft.